The present invention relates generally to medical devices for accessing a blood circulatory system, and particularly to an infusion port subcutaneously implanted within a patient's body for aiding in hemodialysis procedures.
Certain medical procedures require access to a patient's blood circulatory system. Such access has been by way of needle directly into a patient's vein, artery, or a graph incorporated into the blood circulatory system. For example, a person suffering kidney impairment cannot maintain a clean blood supply and must have their blood supply cleansed by hemodialysis, i.e., by use of an artificial kidney machine. In such procedure, the kidney machine is temporarily integrated into the blood circulatory system to remove blood carrying impurities collected from body organs and tissues; filter that blood within the artificial kidney machine; and return the cleansed blood to the circulation system for delivery to the body organs and tissues in the normal course. The blood may be taken from a vein at one point, cleansed, and then returned to the vein at a downstream location. Blood is thereby removed from the body, cleansed, and concurrently returned to the body. The dialysis procedure is performed approximately every other day.
Repeated access to the blood system by needles damages the person's veins and arteries. Devices better withstanding repeated needle access have been placed under the patient's skin. In some cases grafts are used as an access point into the patient's blood circulatory system. Such grafts are typically placed in the person's arm. Unfortunately, repeated access to the arm graft results in skin damage along the arm.
Peritoneal dialysis is an alternative to hemodialysis. Under peritoneal dialysis, a transcutaneous tube fluidly couples at an interior end to the peritoneal cavity and an exterior end of the tube remains outside the person's body. A carrier fluid is delivered by way of this tube into the peritoneal cavity and, by process of osmosis, blood impurities are drawn into the peritoneal cavity. The carrier fluid is then removed from the peritoneal cavity by way of the catheter.
Hemodialysis, i.e., blood exchange by direct coupling to the blood circulatory system, is sometimes performed by use of catheters having one end exterior of the body and the other coupled to the blood circulatory system. Hemodialysis is performed by coupling the exterior ends of the transcutaneous catheters to an artificial kidney machine for access to the body circulatory system to draw blood from and return blood to the person's blood circulatory system.
Use of transcutaneous catheters, however, presents several problems. First of all, such catheters contribute to potential chronic contamination at their exit site. There is a significant risk of infection anytime a catheter is used in transcutaneous service. Furthermore, the personal psychological impact on a hemodialysis patient can be significant, having tubes hanging from one's body does not support a feeling of well-being and healthy outlook.
U.S. Pat. No. 5,090,954 issued Feb. 25, 1992 to applicant herein Gregory L. Geary and entitled Subcutaneous Access Device for Peritoneal Dialysis shows a peritoneal dialysis device including an elongate housing having a needle-penetrable, self-sealing outer membrane surface. The device is subcutaneously located for access in conducting peritoneal dialysis, i.e., the device is available for introducing and removing carrier fluid to and from the peritoneal cavity. The membrane of the subcutaneous device is accessed by needle and an in-dwelling catheter couples the subcutaneous device to the peritoneal cavity.
In other cases, a subcutaneous infusion port penetrated by way of a needle has been proposed for access to a patient's blood circulatory system. U.S. Pat. No. 4,892,518 issued Jan. 9, 1990 to Cupp et al and entitled Hemodialysis proposes a hemodialysis port assembly including a port and a catheter assembly. The two channel catheter assembly shown by Cupp et al is to be implanted in the chest of a patient with the two channel catheter assembly coupled to the subclavian vein. The blood flow in the vein is away from the end of the catheter assembly and each channel of the catheter assembly couples to one chamber of the port. More particularly, an upstream inlet channel of the catheter assembly couples to one chamber of the port while the downstream outlet channel of the catheter assembly couples to the other chamber of the port. In this manner, blood may be drawn from the upstream portion of the subclavian vein by way of the first chamber, cleansed by artificial kidney machine, and returned to the second chamber of the port assembly for delivery by way of the second channel of the catheter assembly at the downstream portion of the subclavian vein. Near the remote end of the catheter assembly, the inlet channel terminates in an inlet valve and the outlet channel terminates in an outlet valve, each valve being described as a "flapper" on which the blood is incident but does not impede the flow of blood in the subclavian vein. The inlet and outlet valves are spaced a sufficient distance to allow removal of impure blood at an upstream point and delivery of cleansed blood at a downstream point. The flapper valves open in response to pressure differentials. At column 1, line 65, it is suggested that the outlet valve should be a two-way valve to conduct the blood out of the vein and to the artificial kidney machine, and also to conduct a solution for cleaning the outlet channel. The inlet valve may also be, it is suggested, a two-way valve to allow cleaning with solution, if needed.
U.S. Pat. No. 4,822,341 issued Apr. 18, 1989 to Colone and entitled Vascular Access Fistula shows an implantable vascular graft communicating percutaneously through a pair of access tubes exterior of the patient's body for dialysis procedures. The external tubes are used for dialysis only after the graft heals. After healing, the tubes are surgically severed so that the apparatus is located entirely subcutaneously. A slidable, subcutaneous shutoff valve is mounted to the graft to isolate the blood flow from the external tubes just before those tubes are severed. During the tube-severing surgical procedure, the valve 22 is accessed via an incision and then permanently closed. The apparatus includes no separate reservoirs or chambers.
U.S. Pat. No. 4,692,146 issued Sep. 8, 1987 to Hilger and entitled Multiple Vascular Access Port shows a subcutaneous access arrangement including two chambers, each penetrable by hypodermic needle and a two channel catheter, each channel being coupled to one of the chambers, for providing an inlet and outlet access to a patient's blood circulatory system.
U.S. Pat. No. 4,710,174 issued Dec. 1, 1987 to Moden et al and entitled Implantable Infusion Port and U.S. Pat. No. 4,673,394 issued Jun. 16, 1987 to Fenton, Jr. et al and entitled Implantable Treatment Reservoir both show subcutaneous reservoirs similar to that shown by Hilger with a reservoir accessible by hypodermic needle and associated catheter for thereby accessing a patient's blood circulatory system.
As may be appreciated, in using an infusion port of the type described above the reservoirs and catheters often fill with the patient's blood supply during use. Certain problems exist with the post-procedure steps taken to clean or flush the device. The blood must be flushed out or removed in some fashion to avoid undesirable blood clotting within the infusion port. As noted above, the Cupp apparatus suggests that flushing be accomplished by introducing fluid into each of the chambers and forcing that fluid out through the catheter channels and into the patient's blood system. In performing such a flushing operation, it may be appreciated that the introduction of flushing solution into the infusion port should be at a conservative rate and pressure and may require some amount of time to suitably flush blood from the device.
Most of the available subcutaneous infusion ports are simply small medication delivery systems. For this purpose, these relatively smaller infusion ports are acceptable. Such ports do not, however, provide sufficient flow capacity to perform hemodialysis. For example, delivery of approximately 100 cc of medication per hour is typical when using a subcutaneous infusion port for medication delivery. Hemodialysis requires, however, much a greater volume of fluid exchange, typically up to 400 cc per minute of blood flow to with the artificial kidney machine. Thus, most infusion ports are not acceptable for the relatively high volume flow required for hemodialysis procedures. According to present medical practice, hemodialysis is not performed by use of infusion ports. Hemodialysis is, according to conventional modern practice, performed using either a graft placed in the patient's arm, or by using transcutaneous catheters having one end maintained external of the person's body for the required frequent access to the blood circulatory system.
It is desirable, therefore, that a subcutaneous infusion port be more readily adapted for high volume capacity required of hemodialysis procedures and well adapted for flushing without the limitation of relatively small flow rates and pressure magnitudes of the cleansing solution.